Renal involvement and the role of Notch signalling in Alagille syndrome. Nat Rev Nephrol. 2013;9:409-418. [PMID: 23752887 DOI: 10.1038/nrneph.2013.102]

Kidney and vascular involvement in Alagille syndrome

Alagille syndrome (ALGS) is an autosomal dominant, multisystemic disease with a high interindividual variability. The two causative genes JAG1 and NOTCH2 are expressed during kidney development, can be reactivated during adulthood kidney disease, and Notch signalling is essential for vascular morphogenesis and remodelling in mice. Liver disease is the most frequent and severe involvement; neonatal cholestasis occurs in 85% of cases, pruritus in 74%, xanthomas in 24% of cases, and the cumulative incidences of portal hypertension and liver transplantation are 66% and 50% respectively at 18 years of age. Stenosis/hypoplasia of the branch pulmonary arteries is the most frequent vascular abnormality reported in ALGS. Kidney involvement is present in 38% of patients, and can reveal the disease. Congenital anomalies of the kidney and urinary tract is reported in 22% of patients, hyperchloremic acidosis in 9%, and glomerulopathy and/or proteinuria in 6%. A decreased glomerular filtration rate is reported in 10% of patients and is more frequent after liver transplantation for ALGS than for biliary atresia. Kidney failure has been frequently reported in childhood and adulthood. Renal artery stenosis and mid aortic syndrome have also frequently been reported, often associated with hypertension and stenosis and/or aneurysm of other large arteries. ALGS patients require kidney assessment at diagnosis, long-term monitoring of kidney function and early detection of vascular complications, notably if they have undergone liver transplantation, to prevent progression of chronic kidney disease and vascular complications, which account for 15% of deaths at a median age of 2.2 years in the most recent series.

Experience and Results of Liver Transplantation in Patients With Alagille Syndrome at Our Center

OBJECTIVES

Alagille syndrome is an autosomal recessive disorder with multisystemic involvement. Patients with Alagille syndrome have many accompanying anomalies such as atypical facial appearance, posterior embryotoxon, butterfly vertebra, cardiac anomalies, and biliary problems. Liver and heart complications can determine the mortality and morbidity of patients with Alagille syndrome. The scarcity of intrahepatic bile ducts leads to cholestatic liver damage. In the heart, although the disease most commonly causes peripheral pulmonary stenosis, patients can present with various structural heart diseases. These cardiac anomalies make intraoperative and postoperative management difficult in patients who need liver transplant. Here, we present 10 cases of liver transplant due to Alagille syndrome.

MATERIALS AND METHODS

From 1988 to the present, our center performed 724 liver transplants, with 366 being pediatric cases; among these, 10 were due to Alagille syndrome. We retrospectively examined patient morphological findings, cardiac pathology, and perioperative complications.

RESULTS

Average weight and age of patients were 11 kg and 4.9 years, respectively. Eight patients had atypical facial appearance, 5 had posterior embryotoxon, and 6 had butterfly vertebra. Portoenterostomy (Kasai procedure) was performed in 3 patients because of suspicion of early biliary atresia. Cardiac pathology was present in 8 patients, with peripheral pulmonary stenosis being the most common (present in 8 patients). One patient had cardiac catheterization, with right ventricular and pulmonary artery pressures measured at 110 and 37 mm Hg, respectively. Two patients required preoperative pulmonary angioplasty. Two patients had double superior vena cava. No complications occurred in any patient during the anhepatic phase with appropriate volume replacement. No patients had early mortality.

CONCLUSIONS

Cardiac anomalies should be identified in patients with Alagille syndrome to minimize complications before liver transplant. If necessary, cardiac catheterization should be performed for pulmonary stenosis. Peripheral pulmonary stenosis does not constitute an absolute contraindication to liver transplant.

UK guideline on the transition and management of childhood liver diseases in adulthood

INTRODUCTION

Improved outcomes of liver disease in childhood and young adulthood have resulted in an increasing number of young adults (YA) entering adult liver services. The adult hepatologist therefore requires a working knowledge in diseases that arise almost exclusively in children and their complications in adulthood.

AIMS

To provide adult hepatologists with succinct guidelines on aspects of transitional care in YA relevant to key disease aetiologies encountered in clinical practice.

METHODS

A systematic literature search was undertaken using the Pubmed, Medline, Web of Knowledge and Cochrane database from 1980 to 2023. MeSH search terms relating to liver diseases ('cholestatic liver diseases', 'biliary atresia', 'metabolic', 'paediatric liver diseases', 'autoimmune liver diseases'), transition to adult care ('transition services', 'young adult services') and adolescent care were used. The quality of evidence and the grading of recommendations were appraised using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system.

RESULTS

These guidelines deal with the transition of YA and address key aetiologies for the adult hepatologist under the following headings: (1) Models and provision of care; (2) screening and management of mental health disorders; (3) aetiologies; (4) timing and role of liver transplantation; and (5) sexual health and fertility.

CONCLUSIONS

These are the first nationally developed guidelines on the transition and management of childhood liver diseases in adulthood. They provide a framework upon which to base clinical care, which we envisage will lead to improved outcomes for YA with chronic liver disease.

Genetics of liver disease in adults

Chronic liver disease stands as a significant global health problem with an estimated 2 million annual deaths across the globe. Combining the use of next-generation sequencing technologies with evolving knowledge in the interpretation of genetic variation across the human genome is propelling our understanding, diagnosis, and management of both rare and common liver diseases. Here, we review the contribution of risk and protective alleles to common forms of liver disease, the rising number of monogenic diseases affecting the liver, and the role of somatic genetic variants in the onset and progression of oncological and non-oncological liver diseases. The incorporation of genomic information in the diagnosis and management of patients with liver disease is driving the beginning of a new era of genomics-informed clinical hepatology practice, facilitating personalized medicine, and improving patient care.

Prenatal diagnosis of polycystic renal diseases: diagnostic yield, novel disease-causing variants, and genotype-phenotype correlations

BACKGROUND

Polycystic renal disease is a frequent congenital anomaly of the kidneys, but research using chromosomal microarray analysis and exome sequencing in fetuses with polycystic renal disease remains sparse, with most studies focusing on the multisystem or genitourinary system.

OBJECTIVE

This study aimed to assess the detection rate of detectable genetic causes of fetal polycystic renal disease at different levels, novel disease-causing variants, and genotype-phenotype correlations.

STUDY DESIGN

This study included 220 fetal polycystic renal disease cases from January 2014 to June 2022. Cases were divided into the following 3 groups: isolated multicystic dysplastic kidneys, nonisolated multicystic dysplastic kidneys, and suspected polycystic kidney disease group. We reviewed data on maternal demographics, ultrasonographic results, chromosomal microarray analysis/exome sequencing results, and pregnancy outcomes.

RESULTS

In our cohort, chromosomal microarray analysis identified 19 (8.6%) fetuses carrying chromosomal abnormalities, and the most common copy number variation was 17q12 microdeletion (7/220; 3.2%). Furthermore, 94 families chose to perform trio-exome sequencing testing, and 21 fetuses (22.3%) were found to harbor pathogenic/likely pathogenic variants. There was a significant difference in the live birth rate among the 3 groups (91/130 vs 46/80 vs 1/10; P<.001). Among 138 live birth cases, 106 (78.5%) underwent postnatal ultrasound review, of which 95 (89.6%) had a consistent prenatal-postnatal ultrasound diagnosis.

CONCLUSION

For both isolated and nonisolated polycystic renal disease, our data showed high detection efficiency with both testing tools. The detection of novel pathogenic variants expands the known disease spectrum of polycystic renal disease-associated genes while enriching our understanding of the genotype-phenotype correlation. Therefore, we consider it feasible to perform chromosomal microarray analysis+exome sequencing testing in fetal polycystic renal disease. Moreover, prenatal-postnatal ultrasound concordance was greater, the live birth rate was higher, and prognosis was better when known genetic disorders were excluded, indicating that genetic testing results significantly influenced pregnancy decisions.

The genetics and pathogenesis of CAKUT

Congenital anomalies of the kidney and urinary tract (CAKUT) comprise a large variety of malformations that arise from defective kidney or urinary tract development and frequently lead to kidney failure. The clinical spectrum ranges from severe malformations, such as renal agenesis, to potentially milder manifestations, such as vesicoureteral reflux. Almost 50% of cases of chronic kidney disease that manifest within the first three decades of life are caused by CAKUT. Evidence suggests that a large number of CAKUT are genetic in origin. To date, mutations in ~54 genes have been identified as monogenic causes of CAKUT, contributing to 12-20% of the aetiology of the disease. Pathogenic copy number variants have also been shown to cause CAKUT and can be detected in 4-11% of patients. Furthermore, environmental and epigenetic factors can increase the risk of CAKUT. The discovery of novel CAKUT-causing genes is challenging owing to variable expressivity, incomplete penetrance and variable genotype-phenotype correlation. However, such a discovery could ultimately lead to improvements in the accurate molecular genetic diagnosis, assessment of prognosis and multidisciplinary clinical management of patients with CAKUT, potentially including personalized therapeutic approaches.

Polycystic kidneys: interaction of notch and renin

Polycystic kidney disease (PKD) is a developmental disorder, which either manifests in early childhood or later in life, depending on the genetic mutation one harbors. The mechanisms of cyst initiation are not well understood. Increasing literature is now suggesting that Notch signaling may play a critical role in PKD. Activation of Notch signaling is important during nephrogenesis and slows down after development. Deletion of various Notch molecules in the cap mesenchyme leads to formation of cysts and early death in mice. A new study by Belyea et al. has now found that cells of renin lineage may link Notch expression and cystic kidney disease. Here, we use our understanding of Notch signaling and PKD to speculate about the significance of these interactions.

Clinical and Genetic Characteristics of Alagille Syndrome in Adults

BACKGROUND AND AIMS

Alagille syndrome (AGS) is an autosomal dominant multisystem disorder caused by mutations in the JAG1 and NOTCH2 genes. AGS has been rarely reported in adult patients, mainly because its characteristics in adults are subtle. The study aimed to improve the understanding of adult AGS by a descriptive case series.

METHODS

Eight adults diagnosed with AGS at our hospital between June 2016 and June 2019 were included in the study. Clinical data, biochemical results, imaging results, liver histopathology, and genetic testing were analyzed.

RESULTS

Three female and five male patients with a median age of 24.5 years at the time of diagnosis were included in the analysis. The clinical manifestations were adult-onset (62.5%, 5/8), cholestasis (50%, 4/8), butterfly vertebrae (62.5%, 5/8), systolic murmurs (12.5%, 1/8), typical facies (12.5%, 1/8), posterior embryotoxon, and renal abnormalities (0/8). Genetic sequencing showed that all patients had mutations, with four occurring in the JAG1 gene and four in the NOTCH2 gene. Six were substitution mutations, one was a deletion mutation, and one was a splicing mutation. Five had been previously reported; but the others, one JAG1 mutation and two NOTCH2 mutations were unique and are reported here for the first time.

CONCLUSIONS

The clinical manifestations highlighted by the current diagnostic criteria for most adults with AGS are atypical. Those who do not meet the criteria but are highly suspicious of having AGS need further evaluation, especially genetic testing.

Applications of human organoids in the personalized treatment for digestive diseases

Digestive system diseases arise primarily through the interplay of genetic and environmental influences; there is an urgent need in elucidating the pathogenic mechanisms of these diseases and deploy personalized treatments. Traditional and long-established model systems rarely reproduce either tissue complexity or human physiology faithfully; these shortcomings underscore the need for better models. Organoids represent a promising research model, helping us gain a more profound understanding of the digestive organs; this model can also be used to provide patients with precise and individualized treatment and to build rapid in vitro test models for drug screening or gene/cell therapy, linking basic research with clinical treatment. Over the past few decades, the use of organoids has led to an advanced understanding of the composition of each digestive organ and has facilitated disease modeling, chemotherapy dose prediction, CRISPR-Cas9 genetic intervention, high-throughput drug screening, and identification of SARS-CoV-2 targets, pathogenic infection. However, the existing organoids of the digestive system mainly include the epithelial system. In order to reveal the pathogenic mechanism of digestive diseases, it is necessary to establish a completer and more physiological organoid model. Combining organoids and advanced techniques to test individualized treatments of different formulations is a promising approach that requires further exploration. This review highlights the advancements in the field of organoid technology from the perspectives of disease modeling and personalized therapy.

Notch signaling pathway: architecture, disease, and therapeutics

The NOTCH gene was identified approximately 110 years ago. Classical studies have revealed that NOTCH signaling is an evolutionarily conserved pathway. NOTCH receptors undergo three cleavages and translocate into the nucleus to regulate the transcription of target genes. NOTCH signaling deeply participates in the development and homeostasis of multiple tissues and organs, the aberration of which results in cancerous and noncancerous diseases. However, recent studies indicate that the outcomes of NOTCH signaling are changeable and highly dependent on context. In terms of cancers, NOTCH signaling can both promote and inhibit tumor development in various types of cancer. The overall performance of NOTCH-targeted therapies in clinical trials has failed to meet expectations. Additionally, NOTCH mutation has been proposed as a predictive biomarker for immune checkpoint blockade therapy in many cancers. Collectively, the NOTCH pathway needs to be integrally assessed with new perspectives to inspire discoveries and applications. In this review, we focus on both classical and the latest findings related to NOTCH signaling to illustrate the history, architecture, regulatory mechanisms, contributions to physiological development, related diseases, and therapeutic applications of the NOTCH pathway. The contributions of NOTCH signaling to the tumor immune microenvironment and cancer immunotherapy are also highlighted. We hope this review will help not only beginners but also experts to systematically and thoroughly understand the NOTCH signaling pathway.

Kidney disease in children with heart or liver transplant

Over the past few decades, there has been increasing recognition of kidney disease in children with non-kidney solid organ transplantation. The risk of kidney disease in children undergoing heart or liver transplantation is higher than the general population as the underlying disease and its associated management may directly impair kidney function. Both heart and liver failures contribute to hypoperfusion and kidney ischemia before patients reach the point of transplant. The transplant surgery itself can often be complicated by acute kidney injury (AKI), which may be further exacerbated by a complicated postoperative course. In the short- and long-term post-transplant period, these children are at risk of acute illness, exposed to nephrotoxic medications, and susceptible to rare but severe infections and immunologic insults that may contribute to AKI and chronic kidney disease (CKD). In some, CKD can progress to kidney failure with replacement therapy (KFRT). CKD and KFRT are associated with increased morbidity and mortality in this patient population. Therefore, it is critical to monitor for and recognize the risk factors for kidney injury in this population and mitigate these risks. In this paper, the authors provide an overview of kidney disease pertaining to heart and liver transplantation in children with guidance on monitoring, diagnosis, prevention, and management.

Beyond Atherosclerosis and Fibromuscular Dysplasia: Rare Causes of Renovascular Hypertension

Renovascular hypertension is one of the most common forms of secondary hypertension. Over 95% of cases of renovascular hypertension are due either to atherosclerosis of the main renal artery trunks or to fibromuscular dysplasia. These two causes of renal artery stenosis have been extensively discussed in recent reviews and consensus. The aim of the current article is to provide comprehensive and up-to-date information on the remaining causes. While these causes are rare or extremely rare, etiologic and differential diagnosis matters both for prognosis and management. Therefore, the clinician cannot ignore them. For didactic reasons, we have grouped these different entities into stenotic lesions (neurofibromatosis type 1 and other rare syndromes, dissection, arteritis, and segmental arterial mediolysis) often associated with aortic coarctation and other arterial abnormalities, and nonstenotic lesions, where hypertension is secondary to compression of adjacent arteries and changes in arterial pulsatility (aneurysm) or to the formation of a shunt, leading to kidney ischemia (arteriovenous fistula). Finally, thrombotic disorders of the renal artery may also be responsible for renovascular hypertension. Although thrombotic/embolic lesions do not represent primary vessel wall disease, they are characterized by frequent macrovascular involvement. In this review, we illustrate the most characteristic aspects of these different entities responsible for renovascular hypertension and discuss their prevalence, pathophysiology, clinical presentation, management, and prognosis.

Beyond Atherosclerosis and Fibromuscular Dysplasia: Rare Causes of Renovascular Hypertension

Renovascular hypertension is one of the most common forms of secondary hypertension. Over 95% of cases of renovascular hypertension are due either to atherosclerosis of the main renal artery trunks or to fibromuscular dysplasia. These two causes of renal artery stenosis have been extensively discussed in recent reviews and consensus. The aim of the current article is to provide comprehensive and up-to-date information on the remaining causes. While these causes are rare or extremely rare, etiologic and differential diagnosis matters both for prognosis and management. Therefore, the clinician cannot ignore them. For didactic reasons, we have grouped these different entities into stenotic lesions (neurofibromatosis type 1 and other rare syndromes, dissection, arteritis, and segmental arterial mediolysis) often associated with aortic coarctation and other arterial abnormalities, and nonstenotic lesions, where hypertension is secondary to compression of adjacent arteries and changes in arterial pulsatility (aneurysm) or to the formation of a shunt, leading to kidney ischemia (arteriovenous fistula). Finally, thrombotic disorders of the renal artery may also be responsible for renovascular hypertension. Although thrombotic/embolic lesions do not represent primary vessel wall disease, they are characterized by frequent macrovascular involvement. In this review, we illustrate the most characteristic aspects of these different entities responsible for renovascular hypertension and discuss their prevalence, pathophysiology, clinical presentation, management, and prognosis.

Beyond Atherosclerosis and Fibromuscular Dysplasia: Rare Causes of Renovascular Hypertension

Renovascular hypertension is one of the most common forms of secondary hypertension. Over 95% of cases of renovascular hypertension are due either to atherosclerosis of the main renal artery trunks or to fibromuscular dysplasia. These two causes of renal artery stenosis have been extensively discussed in recent reviews and consensus. The aim of the current article is to provide comprehensive and up-to-date information on the remaining causes. While these causes are rare or extremely rare, etiologic and differential diagnosis matters both for prognosis and management. Therefore, the clinician cannot ignore them. For didactic reasons, we have grouped these different entities into stenotic lesions (neurofibromatosis type 1 and other rare syndromes, dissection, arteritis, and segmental arterial mediolysis) often associated with aortic coarctation and other arterial abnormalities, and nonstenotic lesions, where hypertension is secondary to compression of adjacent arteries and changes in arterial pulsatility (aneurysm) or to the formation of a shunt, leading to kidney ischemia (arteriovenous fistula). Finally, thrombotic disorders of the renal artery may also be responsible for renovascular hypertension. Although thrombotic/embolic lesions do not represent primary vessel wall disease, they are characterized by frequent macrovascular involvement. In this review, we illustrate the most characteristic aspects of these different entities responsible for renovascular hypertension and discuss their prevalence, pathophysiology, clinical presentation, management, and prognosis.

Beyond Atherosclerosis and Fibromuscular Dysplasia: Rare Causes of Renovascular Hypertension

Renovascular hypertension is one of the most common forms of secondary hypertension. Over 95% of cases of renovascular hypertension are due either to atherosclerosis of the main renal artery trunks or to fibromuscular dysplasia. These two causes of renal artery stenosis have been extensively discussed in recent reviews and consensus. The aim of the current article is to provide comprehensive and up-to-date information on the remaining causes. While these causes are rare or extremely rare, etiologic and differential diagnosis matters both for prognosis and management. Therefore, the clinician cannot ignore them. For didactic reasons, we have grouped these different entities into stenotic lesions (neurofibromatosis type 1 and other rare syndromes, dissection, arteritis, and segmental arterial mediolysis) often associated with aortic coarctation and other arterial abnormalities, and nonstenotic lesions, where hypertension is secondary to compression of adjacent arteries and changes in arterial pulsatility (aneurysm) or to the formation of a shunt, leading to kidney ischemia (arteriovenous fistula). Finally, thrombotic disorders of the renal artery may also be responsible for renovascular hypertension. Although thrombotic/embolic lesions do not represent primary vessel wall disease, they are characterized by frequent macrovascular involvement. In this review, we illustrate the most characteristic aspects of these different entities responsible for renovascular hypertension and discuss their prevalence, pathophysiology, clinical presentation, management, and prognosis.

Mutations in PRDM15 Are a Novel Cause of Galloway-Mowat Syndrome

BACKGROUND

Galloway-Mowat syndrome (GAMOS) is characterized by neurodevelopmental defects and a progressive nephropathy, which typically manifests as steroid-resistant nephrotic syndrome. The prognosis of GAMOS is poor, and the majority of children progress to renal failure. The discovery of monogenic causes of GAMOS has uncovered molecular pathways involved in the pathogenesis of disease.

METHODS

Homozygosity mapping, whole-exome sequencing, and linkage analysis were used to identify mutations in four families with a GAMOS-like phenotype, and high-throughput PCR technology was applied to 91 individuals with GAMOS and 816 individuals with isolated nephrotic syndrome. In vitro and in vivo studies determined the functional significance of the mutations identified.

RESULTS

Three biallelic variants of the transcriptional regulator PRDM15 were detected in six families with proteinuric kidney disease. Four families with a variant in the protein's zinc-finger (ZNF) domain have additional GAMOS-like features, including brain anomalies, cardiac defects, and skeletal defects. All variants destabilize the PRDM15 protein, and the ZNF variant additionally interferes with transcriptional activation. Morpholino oligonucleotide-mediated knockdown of Prdm15 in Xenopus embryos disrupted pronephric development. Human wild-type PRDM15 RNA rescued the disruption, but the three PRDM15 variants did not. Finally, CRISPR-mediated knockout of PRDM15 in human podocytes led to dysregulation of several renal developmental genes.

CONCLUSIONS

Variants in PRDM15 can cause either isolated nephrotic syndrome or a GAMOS-type syndrome on an allelic basis. PRDM15 regulates multiple developmental kidney genes, and is likely to play an essential role in renal development in humans.

Dialogs in the assessment of neonatal cholestatic liver disease

Neonatal cholestatic liver disease is rarely encountered by pathologists outside of specialized pediatric centers and navigating the long list of potential diseases can be daunting. However, the differential diagnosis can be rapidly narrowed through open conversations between the pathologist and pediatric gastroenterologist. The dialog should ideally begin before obtaining the liver biopsy and continue through the rendering of the final pathologic diagnosis. Such dialogs are necessary to first ensure the proper handling of the precious sample and then to allow for synthesis of the clinical, laboratory, imaging, and genetic data in the context of the histologic features seen in the liver biopsy. In this review, we aim to provide a broad template on which such dialogs may be based and pitfalls that may be encountered on both the clinical and pathologic sides. This review will focus on non-biliary atresia etiologies of neonatal cholestasis, including select infectious, genetic, and metabolic entities.

Aberrant Activation of Notch1 Signaling in Glomerular Endothelium Induces Albuminuria

RATIONALE

Glomerular capillaries are lined with a highly specialized fenestrated endothelium and contribute to the glomerular filtration barrier. The Notch signaling pathway is involved in regulation of glomerular filtration barrier, but its role in glomerular endothelium has not been investigated due to the embryonic lethality of animal models with genetic modification of Notch pathway components in the endothelium.

OBJECTIVE

To determine the effects of aberrant activation of the Notch signaling in glomerular endothelium and the underlying molecular mechanisms.

METHODS AND RESULTS

We established the ZEG-NICD1 (notch1 intracellular domain)/Tie2-tTA/Tet-O-Cre transgenic mouse model to constitutively activate Notch1 signaling in endothelial cells of adult mice. The triple transgenic mice developed severe albuminuria with significantly decreased VE-cadherin (vascular endothelial cadherin) expression in the glomerular endothelium. In vitro studies showed that either NICD1 (Notch1 intracellular domain) lentiviral infection or treatment with Notch ligand DLL4 (delta-like ligand 4) markedly reduced VE-cadherin expression and increased monolayer permeability of human renal glomerular endothelial cells. In addition, Notch1 activation or gene knockdown of VE-cadherin reduced the glomerular endothelial glycocalyx. Further investigation demonstrated that activated Notch1 suppression of VE-cadherin was through the transcription factors SNAI1 (snail family transcriptional repressor 1) and ERG (Ets related gene), which bind to the -373 E-box and the -134/-118 ETS (E26 transformation-specific) element of the VE-cadherin promoter, respectively.

CONCLUSIONS

Our results reveal novel regulatory mechanisms whereby endothelial Notch1 signaling dictates the level of VE-cadherin through the transcription factors SNAI1 and ERG, leading to dysfunction of glomerular filtration barrier and induction of albuminuria. Graphic Abstract: A graphic abstract is available for this article.

The Impact of Notch Signaling for Carcinogenesis and Progression of Nonmelanoma Skin Cancer: Lessons Learned from Cancer Stem Cells, Tumor Angiogenesis, and Beyond

Since many decades, nonmelanoma skin cancer (NMSCs) is the most common malignancy worldwide. Basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) are the major types of NMSCs, representing approximately 70% and 25% of these neoplasias, respectively. Because of their continuously rising incidence rates, NMSCs represent a constantly increasing global challenge for healthcare, although they are in most cases nonlethal and curable (e.g., by surgery). While at present, carcinogenesis of NMSC is still not fully understood, the relevance of genetic and molecular alterations in several pathways, including evolutionary highly conserved Notch signaling, has now been shown convincingly. The Notch pathway, which was first developed during evolution in metazoans and that was first discovered in fruit flies (Drosophila melanogaster), governs cell fate decisions and many other fundamental processes that are of high relevance not only for embryonic development, but also for initiation, promotion, and progression of cancer. Choosing NMSC as a model, we give in this review a brief overview on the interaction of Notch signaling with important oncogenic and tumor suppressor pathways and on its role for several hallmarks of carcinogenesis and cancer progression, including the regulation of cancer stem cells, tumor angiogenesis, and senescence.

An Adult Patient with Alagille Syndrome Showing Mainly Renal Failure and Vascular Abnormality without Liver Manifestation

Alagille syndrome is an inherited multisystemic disorder. We herein report an atypical case of a Japanese adult patient with Alagille syndrome. He had been diagnosed with Alagille syndrome as an infant based on a liver biopsy. At 27 years of age, he needed to start hemodialysis therapy, but an arteriovenous fistula was not created because his peripheral blood vessels were too narrow. He also had a recurrent brain infarction due to cerebral vascular stenosis. Alagille syndrome is generally recognized as a pediatric hepatic disease, but general physicians should be aware of its potential existence with renal involvement and vascular abnormalities.

Neonatal liver disease

Neonatal liver disease encompasses many diagnoses, including structural and genetic aetiologies. Many have significant health implications requiring long-term specialist treatment including liver transplantation. Jaundice is a common presenting feature. The ability of health-care professionals to differentiate neonatal liver disease from benign diagnoses such as physiological jaundice is very important. Persistent (more than 2 weeks) of conjugated jaundice always warrants investigation. Severe unconjugated jaundice (requiring prolonged phototherapy) should also be promptly investigated. Recent advances in genomics have enabled previously elusive, precise diagnoses in some patients with neonatal liver disease. This review paper discusses the commoner causes, with a focus on early detection and need for referral to paediatric liver services.

Notch signaling regulates Akap12 expression and primary cilia length during renal tubule morphogenesis

Alagille syndrome patients present with loss of function mutations in either JAG1 or NOTCH2. About 40%-50% of patients have kidney abnormalities, and frequently display multicystic, dysplastic kidneys. Additionally, gain-of-function mutations in NOTCH2 are associated with cystic kidneys in Hajdu-Cheney syndrome patients. How perturbations in Notch signaling cause renal tubular cysts remains unclear. Here, we have determined that reduced Notch signaling mediated transcription by ectopic expression of dominant-negative mastermind-like (dnMaml) peptide in the nephrogenic epithelia from after the s-shaped body formation and in the developing collecting ducts results in proximal tubular and collecting duct cysts, respectively. An acute inhibition of Notch signaling for two days during kidney development is sufficient to disrupt tubule formation, and significantly increases Akap12 expression. Ectopic expression of Akap12 in renal epithelia results in abnormally long primary cilia similar to that observed in Notch-signaling-deficient epithelia. Both loss of Notch signaling and elevated Akap12 expression disrupt the ability of renal epithelial cells to form spherical structures with a single lumen when grown embedded in matrix. Interestingly, Akap12 can inhibit Notch signaling mediated transcription, which likely explains how both loss of Notch signaling and ectopic expression of Akap12 result in similar renal epithelial abnormalities. We conclude that Notch signaling regulates Akap12 expression while also ensuring normal primary cilia length and renal epithelial morphogenesis, and suggest that one aspect of diseases associated with defective Notch signaling, such as Alagille syndrome, maybe mechanistically related to ciliopathies.

Oral manifestations of Alagille syndrome

Alagille syndrome (AGS) is a multisystem disorder classically involving liver and heart failure, characteristic vertebral and facial features and ocular abnormalities. AGS is caused by heterozygous mutations in JAG1 or NOTCH2, with variable phenotype penetrance. We report two cases of AGS in children with tooth defects characterised by green discolouration and hypomineralisation. The role of hyperbilirubinaemia (HB) in this atypical colour, a classical feature of AGS, has been well described. However, it does not totally explain the dental phenotype. As JAG1 and NOTCH2 mutations can affect bone development and considering common physiological pathways between bone and tooth mineralisation, both mutations could participate in this unusual dental phenotype. The role of HB and genetics in the development of the dental phenotype of AGS is discussed in two prototypical cases. Future research should focus on the underlying genetic component of tooth abnormalities.

Notch Pathway and Inherited Diseases: Challenge and Promise

The evolutionary highly conserved Notch pathway governs many cellular core processes including cell fate decisions. Although it is characterized by a simple molecular design, Notch signaling, which first developed in metazoans, represents one of the most important pathways that govern embryonic development. Consequently, a broad variety of independent inherited diseases linked to defective Notch signaling has now been identified, including Alagille, Adams-Oliver, and Hajdu-Cheney syndromes, CADASIL (cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy), early-onset arteriopathy with cavitating leukodystrophy, lateral meningocele syndrome, and infantile myofibromatosis. In this review, we give a brief overview on molecular pathology and clinical findings in congenital diseases linked to the Notch pathway. Moreover, we discuss future developments in basic science and clinical practice that may emerge from recent progress in our understanding of the role of Notch in health and disease.

Notch Signaling and Embryonic Development: An Ancient Friend, Revisited

The evolutionary highly conserved Notch pathway, which first developed during evolution in metazoans and was first discovered in fruit flies (Drosophila melanogaster), governs many core processes including cell fate decisions during embryonic development. A huge mountain of scientific evidence convincingly demonstrates that Notch signaling represents one of the most important pathways that regulate embryogenesis from sponges, roundworms, Drosophila melanogaster, and mice to humans. In this review, we give a brief introduction on how Notch orchestrates the embryonic development of several selected tissues, summarizing some of the most relevant findings in the central nervous system, skin, kidneys, liver, pancreas, inner ear, eye, skeleton, heart, and vascular system.

Aniridia and Axenfeld-Rieger Syndrome: Clinical presentations, molecular genetics and current/emerging therapies

Aniridia and Axenfeld-Rieger Syndrome are related, human ocular disorders that are typically inherited in an autosomal dominant manner. Both result from incorrect development of the eye and have, as their most serious consequences, elevated risk to develop the blinding condition glaucoma. This review will focus on describing the clinical presentations of Aniridia and Axenfeld-Rieger Syndrome as well as the molecular genetics and current and emerging therapies used to treat patients.

A herpesvirus transactivator and cellular POU proteins extensively regulate DNA binding of the host Notch signaling protein RBP-Jκ to the virus genome

Reactivation of Kaposi's sarcoma-associated herpesvirus (KSHV) from latency requires the viral transactivator Rta to contact the host protein Jκ recombination signal-binding protein (RBP-Jκ or CSL). RBP-Jκ normally binds DNA sequence-specifically to determine the transcriptional targets of the Notch-signaling pathway, yet Notch alone cannot reactivate KSHV. We previously showed that Rta stimulates RBP-Jκ DNA binding to the viral genome. On a model viral promoter, this function requires Rta to bind to multiple copies of an Rta DNA motif (called "CANT" or Rta-c) proximal to an RBP-Jκ motif. Here, high-resolution ChIP/deep sequencing from infected primary effusion lymphoma cells revealed that RBP-Jκ binds nearly exclusively to different sets of viral genome sites during latency and reactivation. RBP-Jκ bound DNA frequently, but not exclusively, proximal to Rta bound to single, but not multiple, Rta-c motifs. To discover additional regulators of RBP-Jκ DNA binding, we used bioinformatics to identify cellular DNA-binding protein motifs adjacent to either latent or reactivation-specific RBP-Jκ-binding sites. Many of these cellular factors, including POU class homeobox (POU) proteins, have known Notch or herpesvirus phenotypes. Among a set of Rta- and RBP-Jκ-bound promoters, Rta transactivated only those that also contained POU motifs in conserved positions. On some promoters, POU factors appeared to inhibit RBP-Jκ DNA binding unless Rta bound to a proximal Rta-c motif. Moreover, POU2F1/Oct-1 expression was induced during KSHV reactivation, and POU2F1 knockdown diminished infectious virus production. Our results suggest that Rta and POU proteins broadly regulate DNA binding of RBP-Jκ during KSHV reactivation.

[Liver dysfunction for 8 years with hypertension for 1 week in an 8-year-old girl]

A girl, aged 8 years, developed jaundice and liver dysfunction in the neonatal period, with congenital glaucoma diagnosed on day 5 after birth, hypertension and unusual facies (broad forehead, hypertelorism and deep-set eyes). Cholestasis was the main type of liver dysfunction. Cardiac macrovascular CTA showed stenosis at the abdominal aorta and the beginning of the bilateral renal arteries. Whole exon sequencing revealed a heterozygous frameshift mutation, c.1485delC (absence of cytosine), in exon 12 of the JAG1gene. The girl was diagnosed with Alagille syndrome and was given transaminase-lowering, cholagogic and antihypertensive treatment with multiple drugs. There were significant reductions in serum levels of alanine aminotransferase, aspartate aminotransferase and total bile acid, but blood pressure fluctuated between 102-140 mm Hg/53-89 mm Hg. After renal artery angiography and balloon dilatation angioplasty, the girl was given oral administration of antihypertensive drugs, and blood pressure was controlled at a level of 110-120 mm Hg/60-80 mm Hg. The rare disease Alagille syndrome should be considered when a child has refractory hypertension with the involvement of multiple systems, especially liver dysfunction with cholestasis as the main manifestation. Genetic causes should be analyzed for a early diagnosis.

Modeling Human Digestive Diseases With CRISPR-Cas9-Modified Organoids

Insights into the stem cell niche have allowed researchers to cultivate adult tissue stem cells as organoids that display structural and phenotypic features of healthy and diseased epithelial tissues. Organoids derived from patients' tissues are used as models of disease and to test drugs. CRISPR-Cas9 technology can be used to genetically engineer organoids for studies of monogenic diseases and cancer. We review the derivation of organoids from human gastrointestinal tissues and how CRISPR-Cas9 technology can be used to study these organoids. We discuss burgeoning technologies that are broadening our understanding of diseases of the digestive system.

Whole-Exome Sequencing Enables a Precision Medicine Approach for Kidney Transplant Recipients

BACKGROUND

Whole-exome sequencing (WES) finds a CKD-related mutation in approximately 20% of patients presenting with CKD before 25 years of age. Although provision of a molecular diagnosis could have important implications for clinical management, evidence is lacking on the diagnostic yield and clinical utility of WES for pediatric renal transplant recipients.

METHODS

To determine the diagnostic yield of WES in pediatric kidney transplant recipients, we recruited 104 patients who had received a transplant at Boston Children's Hospital from 2007 through 2017, performed WES, and analyzed results for likely deleterious variants in approximately 400 genes known to cause CKD.

RESULTS

By WES, we identified a genetic cause of CKD in 34 out of 104 (32.7%) transplant recipients. The likelihood of detecting a molecular genetic diagnosis was highest for patients with urinary stone disease (three out of three individuals), followed by renal cystic ciliopathies (seven out of nine individuals), steroid-resistant nephrotic syndrome (nine out of 21 individuals), congenital anomalies of the kidney and urinary tract (ten out of 55 individuals), and chronic glomerulonephritis (one out of seven individuals). WES also yielded a molecular diagnosis for four out of nine individuals with ESRD of unknown etiology. The WES-related molecular genetic diagnosis had implications for clinical care for five patients.

CONCLUSIONS

Nearly one third of pediatric renal transplant recipients had a genetic cause of their kidney disease identified by WES. Knowledge of this genetic information can help guide management of both transplant patients and potential living related donors.

Wilms Tumor After Orthotopic Liver Transplant in a Patient With Alagille Syndrome

We present a case of Wilms Tumor in a patient with Alagille syndrome 10 months after liver transplant. We explore a suggested genetic connection between these 2 diseases. In children with Wilms Tumor, we propose a pathoembryologic explanation for not just the tumor, but also for the cause of associated benign ureteral and renal parenchymal aberrancies that are commonly seen in the Alagille population. We also discuss the diagnostic and therapeutic challenges that can arise in a liver transplant patient with Alagille syndrome who subsequently develops a renal mass.

Well Preserved Renal Function in Children With Untreated Chronic Liver Disease

OBJECTIVES

On the basis of studies with hepatorenal syndrome, it is widely regarded that renal function is impacted in chronic liver disease (CLD). Therefore, we investigated renal function in children with CLD.

METHODS

In a retrospective study of 277 children with CLD, renal function was investigated as glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), measured as clearance of inulin and para-amino hippuric acid or clearance of iohexol. The data were analyzed with regard to different subgroups of liver disease and to the grade of damage.

RESULTS

Hyperfiltration (>+2 SD of controls) was found in the subgroups of progressive familial intrahepatic cholestasis (44%), glycogenosis (75%), and acute fulminant liver failure (60%). Patients with biliary atresia, most other patients with metabolic disease and intrahepatic cholestasis, and those with vascular anomalies and cryptogenic cirrhosis had normal renal function. Decreased renal function was found in patients with Alagille's syndrome (64% < -2 SD). Increased GFR and ERPF was found in patients with elevated transaminases, low prothrombin level, high bile acid concentration, and high aspartate-aminotransferase-to-platelet ratio.

CONCLUSIONS

Most children with CLD had surprisingly well preserved renal function and certain groups had even hyperfiltration. The finding that children with decompensated liver disease and ongoing liver failure had stable kidney function suggests that no prognostic markers of threatening hepatorenal syndrome were at hand. Moreover, estimation of GFR based on serum creatinine fails to reveal hyperfiltration.

The developmental biology of genetic Notch disorders

Notch signaling regulates a vast array of crucial developmental processes. It is therefore not surprising that mutations in genes encoding Notch receptors or ligands lead to a variety of congenital disorders in humans. For example, loss of function of Notch results in Adams-Oliver syndrome, Alagille syndrome, spondylocostal dysostosis and congenital heart disorders, while Notch gain of function results in Hajdu-Cheney syndrome, serpentine fibula polycystic kidney syndrome, infantile myofibromatosis and lateral meningocele syndrome. Furthermore, structure-abrogating mutations in NOTCH3 result in CADASIL. Here, we discuss these human congenital disorders in the context of known roles for Notch signaling during development. Drawing on recent analyses by the exome aggregation consortium (EXAC) and on recent studies of Notch signaling in model organisms, we further highlight additional Notch receptors or ligands that are likely to be involved in human genetic diseases.

Identification of a novel alpha-fetoprotein-expressing cell population induced by the Jagged1/Notch2 signal in murine fibrotic liver

The liver is well known to possess high regenerative capacity in response to partial resection or tissue injury. However, liver regeneration is often impaired in the case of advanced liver fibrosis/cirrhosis when mature hepatocytes can hardly self‐proliferate. Hepatic progenitor cells have been implicated as a source of hepatocytes in regeneration of the fibrotic liver. Although alpha‐fetoprotein (AFP) is known as a clinical marker of progenitor cell induction in injured/fibrotic adult liver, the origin and features of such AFP‐producing cells are not fully understood. Here, we demonstrate a unique and distinct AFP‐expressing cell population that is induced by the Jagged1/Notch2 signal in murine fibrotic liver. Following repeated carbon tetrachloride injections, a significant number of AFP‐positive cells with high proliferative ability were observed along the fibrous septa depending on the extent of liver fibrosis. These AFP‐positive cells exhibited features of immature hepatocytes that were stained positively for hepatocyte‐lineage markers, such as albumin and hepatocyte nuclear factor 4 alpha, and a stem/progenitor cell marker Sox9. A combination of immunohistological examination of fibrotic liver tissues and coculture experiments with primary hepatocytes and hepatic stellate cells indicated that increased Jagged1 expression in activated hepatic stellate cells stimulated Notch2 signaling and up‐regulated AFP expression in adjacent hepatocytes. The mobilization and proliferation of AFP‐positive cells in fibrotic liver were further enhanced after partial hepatectomy, which was significantly suppressed in Jagged1‐conditional knockout mice. Finally, forced expression of the intracellular domain of Notch2 in normal liver induced a small number of AFP‐expressing hepatocytes in vivo. Conclusion: Insight is provided into a novel pathophysiological role of Jagged1/Notch2 signaling in the induction of AFP‐positive cells in fibrotic liver through the interaction between hepatocytes and activated hepatic stellate cells. (Hepatology Communications 2017;1:215‐229)

Translational applications of adult stem cell-derived organoids

Adult stem cells from a variety of organs can be expanded long-term in vitro as three-dimensional organotypic structures termed organoids. These adult stem cell-derived organoids retain their organ identity and remain genetically stable over long periods of time. The ability to grow organoids from patient-derived healthy and diseased tissue allows for the study of organ development, tissue homeostasis and disease. In this Review, we discuss the generation of adult stem cell-derived organoid cultures and their applications in in vitro disease modeling, personalized cancer therapy and regenerative medicine.

Genetic Syndromes Affecting Kidney Development

Renal anomalies are common birth defects that may manifest as a wide spectrum of anomalies from hydronephrosis (dilation of the renal pelvis and calyces) to renal aplasia (complete absence of the kidney(s)). Aneuploidies and mosaicisms are the most common syndromes associated with CAKUT. Syndromes with single gene and renal developmental defects are less common but have facilitated insight into the mechanism of renal and other organ development. Analysis of underlying genetic mutations with transgenic and mutant mice has also led to advances in our understanding of mechanisms of renal development.

Biliary atresia and other cholestatic childhood diseases: Advances and future challenges

Biliary Atresia and other cholestatic childhood diseases are rare conditions affecting the function and/or anatomy along the canalicular-bile duct continuum, characterised by onset of persistent cholestatic jaundice during the neonatal period. Biliary atresia (BA) is the most common among these, but still has an incidence of only 1 in 10-19,000 in Europe and North America. Other diseases such as the genetic conditions, Alagille syndrome (ALGS) and Progressive Familial Intrahepatic Cholestasis (PFIC), are less common. Choledochal malformations are amenable to surgical correction and require a high index of suspicion. The low incidence of such diseases hinder patient-based studies that include large cohorts, while the limited numbers of animal models of disease that recapitulate the spectrum of disease phenotypes hinders both basic research and the development of new treatments. Despite their individual rarity, collectively BA and other cholestatic childhood diseases are the commonest indications for liver transplantation during childhood. Here, we review the recent advances in basic research and clinical progress in these diseases, as well as the research needs. For the various diseases, we formulate current key questions and controversies and identify top priorities to guide future research.

Partitioning-Defective 1a/b Depletion Impairs Glomerular and Proximal Tubule Development

The kidney is a highly polarized epithelial organ that develops from undifferentiated mesenchyme, although the mechanisms that regulate the development of renal epithelial polarity are incompletely understood. Partitioning-defective 1 (Par1) proteins have been implicated in cell polarity and epithelial morphogenesis; however, the role of these proteins in the developing kidney has not been established. Therefore, we studied the contribution of Par1a/b to renal epithelial development. We examined the renal phenotype of newborn compound mutant mice carrying only one allele of Par1a or Par1b. Loss of three out of four Par1a/b alleles resulted in severe renal hypoplasia, associated with impaired ureteric bud branching. Compared with kidneys of newborn control littermates, kidneys of newborn mutant mice exhibited dilated proximal tubules and immature glomeruli, and the renal proximal tubular epithelia lacked proper localization of adhesion complexes. Furthermore, Par1a/b mutants expressed low levels of renal Notch ligand Jag1, activated Notch2, and Notch effecter Hes1. Together, these data demonstrate that Par1a/b has a key role in glomerular and proximal tubule development, likely via modulation of Notch signaling.

Early life predictive markers of liver disease outcome in an International, Multicentre Cohort of children with Alagille syndrome

BACKGROUND & AIMS

Liver disease in Alagille syndrome is highly variable. Many of the patients presenting with severe cholestasis early in life improve spontaneously; 10-20%, however, have progressive disease. It is currently not possible to predict long-term hepatic outcomes in Alagille syndrome. This international, multicentre study was aimed at identifying early life predictors of liver disease outcome.

METHODS

Retrospective clinical, laboratory and radiographic data from a cohort of 144 Alagille syndrome patients, whose long-term hepatic outcomes had been determined a priori based on previously published criteria, were collected.

RESULTS

Sixty-seven patients had mild and 77 had severe hepatic outcome. Univariate analysis demonstrated that cholestasis and fibrosis on biopsy, as well as the presence of xanthomata were significantly different between the groups (P < 0.05 for all). Mixed model analysis revealed that total serum bilirubin and serum cholesterol were also associated with outcome (P = 0.001 and P = 0.002, respectively). Graphical representation of the data revealed a change in total bilirubin levels between 12 and 24 months of age in the mild group. Recursive partitioning identified a threshold for total bilirubin of 3.8 mg/dl (65 mmol/L) in that age-frame that differentiated between outcomes. A multivariable logistic regression model was developed using fibrosis, xanthomata and the total bilirubin cut-off of 3.8 mg/dl (65 mmol/L), which generated an area under the ROC curve of 0.792.

CONCLUSIONS

The long-term hepatic outcomes of patients with Alagille syndrome can be predicted based on serum total bilirubin between the ages of 12-24 months combined with fibrosis on liver biopsy and the presence of xanthomata on physical examination.

Tumor necrosis factor-alpha up-regulates expression of Jagged-1 and induces epithelial-mesenchymal transition in rat cholangiocytes in vitro

AIM: To investigate the role of tumor necrosis factor-alpha (TNF-α) in the epithelial-mesenchymal transition (EMT) process in rat cholangiocytes in vitro.

METHODS: Primary rat cholangiocytes were treated with TNF-α (10 ng/mL) alone, TNF-α plus nuclear factor kappa B (NF-κB) inhibitor PDTC (50 µmol/L), or PDTC alone for 72 h. The expression of Jagged-1, mesenchymal markers [fibroblast-specific protein-1 (FSP-1), Vimentin and α-SMA] as well as epithelial marker CK19 was detected by Western blot. NF-κB binding activity was measured by EMSA. Migration ability and morphological changes of cholangiocytes were also examined.

RESULTS: In the TNF-α alone group, the protein levels of Jagged-1, FSP-1, Vimentin and α-SMA were up-regulated compared to control cells, whereas the expression of CK19 was down-regulated. The migration ability of cholangiocytes was increased and their shape changed from stone-like to fiber-like. For the TNF-α plus PTCD group and the PTCD alone group, no significant changes in EMT markers as well as migration ability were observed compared to control cells.

CONCLUSION: TNF-α is able to increase the expression of Jagged-1 and induce EMT in rat cholangiocytes in vitro possibly through activation of NF-κB signaling.

[Fibromuscular dysplasia of renal arteries]

Fibromuscular dysplasia is non-atherosclerotic, non-inflammatory disease of the medium caliber arteries causing segmental stenosis, and sometimes aneurysm and/or dissection. Renal involvement is either asymptomatic or revealed by hypertension, rarely acute complications (renal infarction/hemorrhage). Cross-sectional imaging or angiography differentiates multifocal fibromuscular dysplasia (pearl necklace appearance) and focal fibromuscular dysplasia (tubular stenosis). Several differential diagnoses are to be mentioned. Carotid and vertebral involvement are possible. Smoking cessation must be encouraged. Selected patients benefit from renal revascularization. The best indications are recent or resistant hypertension, and progressive renal atrophy. Angioplasty without stent revascularization is the technique of choice in purely stenotic forms.

Jagged1 (JAG1): Structure, expression, and disease associations

Jagged1 (JAG1) is one of the 5 cell surface ligands that functions primarily in the highly conserved Notch signaling pathway. Notch signaling plays a critical role in cellular fate determination and is active throughout development and across many organ systems. The classic JAG1-NOTCH interaction leads to a cascade of proteolytic cleavages resulting in the NOTCH intracellular domain being transported into the nucleus where it functions to activate downstream transcription of target genes. JAG1 mutations have been associated with several disorders including the multi-system dominant disorder Alagille syndrome, and some cases of tetralogy of Fallot (although these may represent variable expressivity of Alagille syndrome). In addition, variations in JAG1 have been found to be associated with multiple types of cancer including breast cancer and adrenocortical carcinoma. Alagille syndrome, which primarily affects the liver, heart, skeleton, eye, face, kidney and vasculature is caused by loss of function mutations in JAG1, demonstrating that haploinsufficiency for JAG1 is disease causing, at least in these tissues. Expression and conditional gene knockout studies of JAG1 (Jag1) have correlated with tissue-specific disease phenotypes and have provided insight into both disease pathogenesis and human development.

Long-term culture of genome-stable bipotent stem cells from adult human liver

Despite the enormous replication potential of the human liver, there are currently no culture systems available that sustain hepatocyte replication and/or function in vitro. We have shown previously that single mouse Lgr5+ liver stem cells can be expanded as epithelial organoids in vitro and can be differentiated into functional hepatocytes in vitro and in vivo. We now describe conditions allowing long-term expansion of adult bile duct-derived bipotent progenitor cells from human liver. The expanded cells are highly stable at the chromosome and structural level, while single base changes occur at very low rates. The cells can readily be converted into functional hepatocytes in vitro and upon transplantation in vivo. Organoids from α1-antitrypsin deficiency and Alagille syndrome patients mirror the in vivo pathology. Clonal long-term expansion of primary adult liver stem cells opens up experimental avenues for disease modeling, toxicology studies, regenerative medicine, and gene therapy.

Glomerular development--shaping the multi-cellular filtration unit

The glomerulus represents a highly structured filtration unit, composed of glomerular endothelial cells, mesangial cells, podocytes and parietal epithelial cells. During glomerulogenesis an intricate network of signaling pathways involving transcription factors, secreted factors and cell-cell communication is required to guarantee accurate evolvement of a functional, complex 3-dimensional glomerular architecture. Here, we want to provide an overview on the critical steps and relevant signaling cascades of glomerular development.

Alagille, Notch, and robustness: why duplicating systems does not ensure redundancy

The mammalian kidney forms from several populations of progenitors that only persist during embryogenesis. The epithelial nephron progenitors reside in the cap mesenchyme (CM), whereas mesangial and endothelial cell progenitors reside in the neighboring stromal mesenchyme (SM). After a ureteric bud (UB) signal induces mesenchymal to epithelial transition of some CM cells, they form a nascent epithelial ball (a renal vesicle, or RV) that requires signals mediated by Notch receptors to separate proximal from distal fates. Two Notch receptors (Notch1 and Notch2) and two ligands (Jagged1 and Delta1) are expressed in the RV. Notably, instead of providing sufficient redundancy to ensure that losing any one allele will be inconsequential to human health, a reduction in the dose of one ligand (Jagged1) or one receptor (Notch2) is causally associated with a rare developmental syndrome (Alagille syndrome, or ALGS) affecting eye, kidney, liver, and craniofacial development. Here we discuss our current understanding of the molecular basis for the nonredundant role of Notch2 in this process, and the avenue for new therapeutic strategies that these insights provide.